Reconstruction of the Radioactive Contamination Occurring in the Environment in Primorskii Krai as a Result of a Nuclear Accident on a Submarine in Bukhta Chazhma

The trajectory of a radioactive cloud formed above the Dunai Peninsula, Ussuriiskii Zaliv, Primorskii Krai, and the border area of China as a result of a nuclear accident in Bukhta Chazma in 1985 was reconstructed. The population–cloud contact time and the radioactive fallout density of the primary dose-forming radionuclides are estimated and the obtained results are compared with the admissible norms and the background. As a result of radioactive decay, scattering, and wash-out by atmospheric precipitation the volume activity of the dose-forming radionuclides in the ground layer of the atmosphere decreased by a factor of 105–106 over the passage time of the radioactive cloud starting from 1 km away from the site of the accident to the tip of Ussuriiskii Zaliv (60 km) and by a factor of 107–108 up to 400 km. The greatest contamination of Ussuriiskii Zaliv was noted in the uninhabited Cape Sedlovidnyi, located near the coastal radioactive track formed above the Dunai Peninsula after the accident. The radioactive fallout density increased by 3.8 kBq/m2 and the dose rate by 0.03 μSv/h, and in all other locations these indicators did not exceed 0.7–1 kBq/m2 and 0.01 μSv/h, respectively. These values turned out to be lower than the global fallout of 137Cs – 4.4 ± 0.7 kBq/m2 and the natural γ-background 0.14 ± 0.06 μSv/h. On the territory of Primorskii Krai and in the border area of China, the contamination did not exceed 0.01–1% of the background. At all stages of the accident, 60Co determined 95–99% of the long-time contamination of the environment.